The airline, the fourth-biggest based in Europe, tells Reuters it made the move to try and keep its crew appearance "artless and well-groomed with makeup in pastel tones." Turkish suggested that the more understated look would help attendants communicate with customers, according to Reuters.

"As a consequence of our current cabin uniforms not including red, dark pink, et cetera, the use of lipstick and nail polish in these colors by our cabin crew impairs visual integrity," Turkish says in a statement.

"And the cabin crew is not happy about it," CNN says. "Outrage spilled into social media, sparking newspapers columns and a movement after Turkish Airlines announced the new dress code this week," CNN adds.

Reuters writes the airline's move has "struck a nerve among secular Turks worried the country is becoming more Islamic."

"This new guideline is totally down to Turkish Airlines management's desire to shape the company to fit its own political and ideological stance," Atilay Aycin, president of Turkish Airlines' Hava-Is labour union, is quoted as saying by Reuters. "No one can deny that Turkey has become a more conservative, religious country."

Turkey's population is mostly Muslim, but the nation has a secular constitution and is a member of NATO and a candidate to join the European Union.

Still, for Turkish Airlines, the lipstick and nail polish flap isn't the first for the airline regarding its attendants.

Reuters notes the airline "caused a stir this year when newspapers published mock-ups of an Ottoman-style uniform for women." AFP writes the "ankle-length dresses and Ottoman-style fez caps" shown in the images "were criticized as too conservative." Travel-focused website Jaunted.com posts the images, describing the proposed uniforms as "the opposite of scandalous."

Also this year, Turkish said in a Feb. 27 statement that it would has restrict alcohol service to business class on some domestic routes and eliminate it on routes to eight conservative Middle East nations.